1. Field of the Invention
This invention relates generally to devices for removing gases from liquids. The device can efficaciously be used as a part of a chromatography system for removing gases from elution solutions, although its application is not so restricted.
2. Description of the Prior Art
In many industrial systems or research processes, it is necessary to remove gases from a liquid to optimize performance of the system or process. For example, in liquid chromatography, elution solutions frequently contain entrained gas bubbles and dissolved gases after passing through an absorption column. Prior to analysis of the elution solution, it is beneficial to deaerate the solution. Liquids requiring degasification may be at ambient pressure, at a positive pressure, or at a subatmospheric pressure.
A variety of devices have been employed for the purposes of removing gas bubbles from liquids. For example, U.S. Pat. No. 4,643,713 teaches a venous reservoir for use in a blood treatment system, such as might be employed during cardiopulmonary surgery for removing gas bubbles from blood being recirculated to the patient undergoing surgery. The device primarily consists of a vented chamber constructed of flexible materials through which the blood flows. Blood enters one end of the chamber and exits at the opposite end of the chamber. As the blood flows into the chamber its velocity decreases and it expands rapidly, allowing gas bubbles to migrate out of the liquid to the vent. The vent is positioned on the upper portion of the chamber into which the blood flows to allow the gas bubbles that are removed from the blood to pass out of the chamber to the atmosphere. The chamber is shaped to assist in the collection of gas bubbles at its top and to direct fluid flow to the outlet. The chamber does not, however, have any interior baffling or flow-directing means, and the vent control is manually operated. The chamber is normally continually filled with blood and there is no sensing or automatic control of the vent valve relative to the blood level in the chamber.
A related device is taught in U.S. Pat. No. 4,734,269, relating to a venous reservoir bay with an integral high-efficiency bubble removal system. This device also has application in blood treatment systems to remove gas bubbles. In addition to the liquid flowing into a chamber where it can expand and its flow rate can slow, this device incorporates a filter system through which the blood flows. The filter device assists in the removal of the entrained gases, which are then vented through a vent fitting located at the upper portion of the chamber. Additionally, another vent is located at the upper portion of the chamber, but outside the filter device. Normal flow through the device results in blood flowing into the chamber, up and through the filter device, and then exiting the chamber at the opposite end. The device is provided with a bypass flow channel to allow the liquid to continue flowing should the filter become clogged.
In some applications, such as liquid chromatography, it is not desirable to pass the liquid that one desires to deaerate through a filter mechanism, as the filtering may remove or alter the composition of the elution liquid. Additionally, filtering typically requires that a greater pressure head be used to urge the liquid through the deaeration device, particularly at higher flow rates, and depending on the pressures, temperatures, and the characteristics of the liquids involved, cleaning or replacement of filters can be difficult and time consuming.
In some situations the pressures involved in the systems requiring deaeration make it impracticable to have a system continuously vented to atmospheric pressure, as is taught by the above-referenced patents, as the pressure in the system would cause the liquid itself to pass through the vent connection.
It is an object of the present invention to provide an improved deaeration apparatus.
It is a further object of this invention to provide a deaeration apparatus that can efficaciously deaerate liquids over a range of pressures, and that can maintain the pressure in the deaeration apparatus in a selected range.
Another object of the invention is to provide an apparatus that will remove gas bubbles and also dissolved gases.
Other objects and advantages will be more fully apparent from the ensuing disclosure and appended claims.